linux-kernel - [PATCH 3.16 314/346] i2c: mux: pca954x: retry updating the mux selection on failure

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Message-ID: <lsq.1479082460.5407563@decadent.org.uk>
Date:   Mon, 14 Nov 2016 00:14:20 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Peter Rosin" <peda@...ntia.se>,
        "Wolfram Sang" <wsa@...-dreams.de>
Subject: [PATCH 3.16 314/346] i2c: mux: pca954x: retry updating the mux
 selection on failure

3.16.39-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Peter Rosin <peda@...ntia.se>

commit 463e8f845cbf1c01e4cc8aeef1703212991d8e1e upstream.

The cached value of the last selected channel prevents retries on the
next call, even on failure to update the selected channel. Fix that.

Signed-off-by: Peter Rosin <peda@...ntia.se>
Signed-off-by: Wolfram Sang <wsa@...-dreams.de>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/i2c/muxes/i2c-mux-pca954x.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -161,7 +161,7 @@ static int pca954x_select_chan(struct i2
 	/* Only select the channel if its different from the last channel */
 	if (data->last_chan != regval) {
 		ret = pca954x_reg_write(adap, client, regval);
-		data->last_chan = regval;
+		data->last_chan = ret ? 0 : regval;
 	}
 
 	return ret;